Change how we check that we have a suitable 'make'

We now check in the same way that the testsuite does.

ghc.mk

@@ -76,6 +76,23 @@
 
 default : all
 
+
+##################################################
+# Check that we have a new enough 'make'
+
+HAVE_EVAL := NO
+$(eval HAVE_EVAL := YES)
+
+ifeq "$(HAVE_EVAL)" "NO"
+$(error Your make does not support eval. You need GNU make >= 3.81)
+endif
+
+ifeq "$(abspath /)" ""
+$(error Your make does not support abspath. You need GNU make >= 3.81)
+endif
+##################################################
+
+
 # Catch make if it runs away into an infinite loop
 ifeq      "$(MAKE_RESTARTS)" ""
 else ifeq "$(MAKE_RESTARTS)" "1"

mk/tree.mk

 
-ifneq "$(findstring 3.7, $(MAKE_VERSION))" ""
-ifeq "$(findstring 3.79.1, $(MAKE_VERSION))" ""
-$(error GNU make version 3.79.1 or later is required.)
-endif
-endif
-
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 #
 #	Layout of the source tree